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MCN speaks to Triumph Infor Rocket Streamliner designers

Published:
21 September 2016

After reaching 274.2mph during a practice run in August, Guy Martin and Triumph returned to the Bonneville Salt Flats, Utah last week with their sights set on 400mph and a new record in the Division C (Streamlined Motorcycle) - Type V class.

Unsurprisingly, there's a lot of time, effort, technology and electronics that go into a 1000bhp streamlined motorcycle, so we spoke to crew chief/designer Matt Markstaller and Motec Electronics Expert James Whistler about creating and running such a machine.

Matt Markstaller

Did you produce the power first?We’ve run the tuned engines on a regular dyno with them housed in a regular Rocket, just like you would a conventional bike. Then again once on the chassis, with the two engines combined. We’ve run the Streamliner on a specialist car dyno, the long wheelbase wasn’t a problem so we know the power and torque of the engines combined. We looked at chassis simulation to limit weave and wobble.

We worked with Dynomotion in Italy who work with many of the MotoGP teams. We can try different simulations to get the balance right, wheelbase and head angle, that way we know we have something stable using algorithms before we go ahead for real.

Is it hard to balance?Balancing the bike is relatively easy. We have 15lb of lead on the right side because the Rocket engines are slightly heavier on one side than the other. The static balance is rather easy to be honest. You want weight over the rear for traction, but you don’t want the front to be too light as you need weight over the front for stability. Then it’s the aerodynamics – which is the hard part.

So the faster you go the more stable it is?If I remember right off the top of my head, the worst wobble comes in just over 100mph, then weave starts to creep in around 200mph or just before. Once you are above 200mph it’s actually more stable, according to the computer.

So the dangerous part is running at sub-200mph?For stability you could say that, as once above 200mph you should have the stability but then once above 300mph approaching 400mph you are then pushing the mechanicals, tyres for example and the wind can become an issue – along with a thousand other things.

What is it like working with Guy?At first we were a little concerned as originally the Streamliner was designed for a shorter rider and we were concerned he might not fit in, but he gets wedged in there. Guy is amazing to work with he has no fear, he just wants to go for it. If we say ‘let’s go flat-out’ there’s no doubt he will go for it.

Guy is used to road racing, where you don’t have the best handling bike because of the conditions, jumps, bumps etc. Our bike isn’t the best handling, but Guy just jumps in and gets on with it. He is used to just going for it. For some riders it can take a week of practice to ride past the weave and wobble – it took Guy 15 minutes.

James Whistler

Apart from controlling the fuelling what else are you measuring?We’ve got just about everything you want to measure all covered: ground speed, GPS speed, drive speed all the engine data you’ll ever need, oil temp, water temp, intake temp, compartment temp, pre-turbo temp, air pressure... the list goes on and on. And that is for each engine. We also measure wheel speed and suspension travel front and back, and full pitch, yaw and roll.

Do you have traction control?We have full traction control. It worked by retarding the ignition for a short while, then we go to a cut ignition setting – but we really don’t want that, as we’re filling up a big exhaust with wasted fuel and air. We try to simply retard the ignition as much as possible to try and get it back in line, but we also have to allow for some slip – it’s inevitable.

How much slip does the system allow?The rear wheel spins quicker than the front. We are looking at around 430mph rear wheel speed for a 400mph ground speed. If the front is doing 400 then the rear will be 420-430mph by our estimations. Around a 4% slip is what we are expecting. You have to remember we have no real downforce.

Guy controls the power but I’m trying to give him some help, as this has the potential for over 1000bhp on a slick tyre. Guy actually starts by rolling the power then goes all in and I try to help when he hits a soft bit of the track for example. We are aiming for a constant 0.3G of acceleration.

Do you also measure G on de-acceleration?Yes we can measure that. When the parachutes open we see about 1.5G negative, then it starts to drop off. The ’chutes do a really good job of stopping the bike. On a good racebike on track we’d see about the same 1.5G, F1 cars can go up to 5G, so it’s not that much.

Is Guy always upright?He usually has just a fraction of lean all the way down the course. It’s back and forth depending on acceleration and braking but he is never 100% upright – or very rarely.